Heretofore, a compression ratio changing mechanism for changing the compression ratio (or the mechanical compression ratio), defined as the ratio of the volume of the cylinder (cylinder volume) and the combustion chamber volume, by changing the combustion chamber volume mechanically has been known, as disclosed in, for example, Japanese Patent Application Laid-Open No. 60-230522. In internal combustion engines equipped with a compression ratio changing mechanism, it is possible to achieve an increase in the output power and gas mileage and prevention of knocking with a high degree of balance by changing the compression ratio in accordance with operating states.
Japanese Patent Application Laid-Open No. 1-106958 discloses a technology of controlling, in an internal combustion engine a variable compression ratio equipped with a plurality of cylinders, ignition time or fuel supply quantity in each of the cylinders based on the pressure in the cylinder at a time when combustion is not performed.
Japanese Patent Application Laid-Open No. 1-45965, Japanese Registered Utility Model No. 2510247 and Japanese Patent Application Laid-Open No. 2-40056 disclose methods of controlling ignition timing etc. when the compression ratio is changed.
Japanese Patent Application Laid-Open No. 63-18142 and Japanese Domestic Re-publication of PCT International Application No. 97-13063 discloses technologies of reducing the effective compression ratio in an internal combustion engine having a variable valve actuation mechanism and a compression ratio changing mechanism by controlling the variable valve actuation mechanism when knocking is detected.